Fix autowidth on statgl_plot

[emilmalta]

• statgl_plot() removes the default Highcharts border around bars and
  columns (borderWidth = 0). The 1 px outline was visually noisy,
  particularly in dark mode where the contrast made it prominent.

• statgl_plot() now reflows the Highcharts chart inside a
  requestAnimationFrame callback after render. Fixes charts appearing
  at ~3/4 width when lazy-rendered inside a shorty shortcode
  (IntersectionObserver / <template> path) until the window is resized.